Protective switch



June 7, 1955 J. ELLENBERGER 2,710,321

PROTECTIVE SWITCH Filed April le, 1954 Je@ te@ Lnited Patented June 7, l

PRTECTll/E SWETCH .ialroh Ellenberger, Altdof, near Blumberg, Germany,

to Ellenberger @z Poensgen G. rn. b. H., a corporation of Germany-pplication April i6, w54, Serial No. 423,739

Claims priority, application Germany April 21, 1953 9 Claims. (Cl.23d-414) The present invention relates to improvements in protectiveswitches, and more particularly to multiple-pole switches for electricmotors and other electric apparatus.

It is the object of the invention to design a new multiplepole thermalcut-out witch for a maximum load and ot minimum size which will safelyprotect an electric motor or other electrical apparatus or appliancefrom overcurrents, which may be caused, for eXar ple, by overheatedbearings or any other occurrences.

A feature of the invention consists in providing a multiple-pole protec've switch of novel des fn and very small dimensions, in which a movablecontact bridge is provided for each circuit, which is safely retained inthc onposition by a catch or detent on the movable end of a bimetalstrip, and which is quickly released under spring pressure to interruptthe current if an overload occurs and the birnetal strips are bent oythe resulting heat, or if the temperat 1re in or around the switchshould exceed certain value for any other reasons.

Another feature of the invention consists in providing the movablecontact bridges and the opposed stationary contacts each on a commonsupporting element parallel to each other, and in mounting each switchelement so as to be turned l80 relative to the adjacent elements.

Further features of the invention consist in mounting the individualswitch elements, and especially the contact i bridges, adjacent eachother on a common contact plate, and in providing all of the elementswhich effect the movement of such contact plate within the area of theswitch base on which the stationary contacts are mounted.

Another feature of the invention consists in mounting the contact plateso as to be freely movable and without any special guiding means, and toprevent it from tilting under the pressure of the release spring byholding it at several points which are symmetrically arranged relativeto the point of application of the release spring by detents mounted onthe free or movable ends of bimetal strips. Such freely movable mountingof the contact plate results in an extremely simple and compact designol the entire switch, and an easy, reliable operation thereof at alltimes.

An additional feature ot the invention resulting from such compactdesign of the novel switch and the fact that it is made of heatresistant material consists in its application not merely for protectingan electrical machine or apparatus from overcurrents, but also fromexcessive heat, caused, for example, by overheated bearings or otherreasor. in which event the circuit alter may be mounted in the immediatevicinity of the respective machine part to be controlled, for example,withithe housing of the electric motor. Naturally, the application ofthe new switch is not restricted to electric motors but it may also beused in any other place or be built into any other machine or apparatus,especially if a protective switch of very small dimensions is desired.

Further objects, features, and advantages or the present invention willappear from the following detailed description thereof and theaccompanying drawings, in whichlii Fig. l shows a longitudinal sectionthrough a protective switch according to the invention, taken along lineI-I of Fig. 2;

Fig. 2 shows a section through the switch taken along line II-H of Fig.l;

Fig. 3 is a top view upon the mounting strap and the contact plate;

Fig. 4 is a top view upon the base plate and the contact clips thereon;

Fig. 5 is a top view of the entire switch in closed position;

Fig. 6 is a side view of the switch with the front wall or" the coverremoved for better illustration;

Fig. 7 is a diagrammatic illustration of the use of the switch asapplied to a three-phase A. C. motor in star connection; while 8 is anillustration similar to Fig. 7 for a delta connection.

Referring to the drawings, the base plate l, preferably Consisting ofceramic material, carries on its upper surface the spring contact clips3 and the bimetal strips 4, and on its lower surface the terminals S. Asshown especially in Fig. 2, each of the bimetal strips d has coiledthereon a resistance wire 6 which terminates below the contact plate 7.Spring clips T2, the lower end of the resistance coils 6, and theterminals 5 are electrically connected, as well as secured to base platel, by bolts 2 which also support the bimetal strips 4 which, however,are electrically insulated therefrom. i`he upper end ot' each resistancecoil e is connected to a lug with a detent thereon and mounted on thebimetal strip 4 which extends upwardly and beyond such lug or dere-nt 8with its free end 9 passing through an aperture in an insulatingy plate10. Plate it) is arranged so as to be freely movable and is preventedfrom sliding olf t'ne free ends 9 of the binietal strips 4 by a mountingstrap il which, in turn, is secured to the base plate l and the upperpart of which extends closely above the insulating plate l0. The contactplate 7 has bolted thereon the Contact bridges i2 with downwardlyprojecting contact ngers i3 which are adapted to iit into, and engagewith, the free ends of the spring clips 3, The lateral studs ldextending downwardly from the contact plate 7 act as centering means forsecuring the coil springs l5. The contact plate 7 has further rigidlyand centrally mounted thereon a Control button L; which is forcedupwardly by a coil spring i7 which rests on the upper surface or' theretaining strap ll. The cover 1S is removably secured to the strap l1'by two screws i9 and has a central aperture for the control button 16,as well as a slide button 2t) with knurls 2l on one side and the symbolof an arrow on the other side, i, e. the side facing the control buttoni6. The slide button 2l) is preferably made ot a single piece ofmaterial and secured to the cover i8 by means 0 a spring ring 23 so asto be laterally slidable thereon.

lf in the operation of the switch the button i6 is depressed from theposition shown in Fig. l to that shown in Fig. o to switch on thecurrent by engaging the contacts l?, and 3, the cam surfaces 24 on thecontact plate 7 will bend the elements 8 towart the left until the uppersurface of the contact bridge l2 engages with the detents thereon,permiting them to spring back to their orialnal position, therebyretaining the contact plate against the action of the springs and i7 inthe position shown in Fig. 6. if the bimetal strip L- is then heatedbeyond a certain temperature either by the resists :e coil 6 or for anyother cause, the upper, free ends thereof will bend toward the leftuntil the detents of the elements el release the contact bridge 7. Thesame result may also be obtained by pushing the slide button Ztl in thedirection shown by the arrow 22, i. e. toward the control button 16. Thelower, ngerlike projection 2S of the slide button thereby engages theedge of the insulating plate 1t) and bends the free ends 9 ot thebimetal strips 4, which are guided by the plate 1t), toward the lett inthe same manner as if such bending were caused by heating the bimetalstrips d. lf, however, contrary to the manual operation of the switch bythe slide button 2G, the bimetal strips f:- are bent by being heated bythe resistance coils 6 to disengage the detents 8 from the contactbridge 12 to release the plate '7 and disconnect the contacts 13 and 3,the current may not again be switched on until the temperature in oraround the switch has returned to normal and the bimetal strips 4 haveregained their normal position.

For conning the adjacent contact elements within the smallest possiblespace, they preferably are turned 180 relative to each other. Also, itis advisable to malte both the base plate 1 as well as the contact plate7 of ceramic material, and the insulating plate 19, used for manuallydisconnecting the switch, likewise of heat resistant materiat.

While the foregoing description sets forth in detail what l regard asthe preferred embodiment of my invention, it is to be understood thatnumerous changes may be made therein without departing from the spiritand scope of the invention as defined in the appended claims.

Having thus described my invention, what I claim as new is:

l. A multipie-pole protective switch comprising, in combination, astationary base, stationary contacts mounted on said base, a bimetalstrip for each circuit having one end mounted on said base, means forheating said bimetal strips, a detent carried on each of said bimetalstrips near the free end thereof, a movable bridge element, contactsmounted on said element to cooperate with said stationary contacts, saidmovable and corresponding stationary contacts being turned 180 relativeto the adjacent contacts, a spring tending to force said bridge and thecontacts thereon to the off-position, resilient means for maintainingsaid bridge always substantially parallel with said base, means fordepressing said bridge to engage the contacts thereon with thecorresponding stationary contacts and simultaneously to engage saiddetents with said bridge to retain the same in the on-position, and forsimultaneously connecting said heating means, each of said detentsadapted to release said bridge when said bimetal strips are heatedbeyond a certain temperature and are thereby bent so as to disconnectsaid corresponding contacts under the pressure of said spring.

2. A multiple-pole protective switch comprising, in combination, astationary base, stationary contacts on said base, a bimetal strip foreach circuit mounted on said base, means for heating said bimetal strip,a detent on each of said bimetal strips near the free end thereof,

a movable bridge element, contacts mounted on said element to cooperatewith said stationary contacts, said movable and stationary contactsbeing turned 180 relative to the adjacent contacts, a central button fordepressing said movable bridge to engage the contacts thereon with thecorresponding stationary contacts and simultaneously to engage saiddetents with said bridge to retain the same in the ori-position, and forsimultaneously connecting said heating means, said detents adapted torelease said bridge when said bimetal strips are being heated beyond acertain temperature, a central spring tending to force said bridge andthe contacts thereon to the oit-position, and a plurality of springs formaintaining said bridge always substantiaily parallel with said base.

3. A multiple-pole protective switch comprising, in combination, astationary base, stationary contacts mounted on said base, a bimetalstrip for each circuit mounted on said base, means mounted on saidbimetal strips for heating the same, a detent on each of said bimetalstrips, said strips having a free end extending upwardly and beyond saidheating means and detents,

a movable Contact bridge element, contacts mounted on said element tocooperate with said stationary contacts, resilient means tending toforce said bridge and contacts thereon to the off-position and formaintaining said bridge always substantially parallel with said base, acentral button for depressing said movable bridge to engage the contactsthereon with the corresponding stationary contacts and simultaneously toengage said heating means, said detents adapted to release said bridgewhen said bimetal strips are being heated beyond a certain temperature,an insulating plate having apertures, the free ends of said bimetalstrips extending through said apertures so as to move freely in onedirection when said strips are bent by being heated, and means forshifting said insulating plate to bend said strips to disengage saiddetents, release said bridge, and disconnect said contacts independentlyof said heating means.

4. A multiple-pole protective switch comprising, in combination, astationary base, mounted on said base, a bimetal strip for each circuitmounted on said base, means mounted on said bimetal strips for heatingthe same, a detent on each of said bimetal strips, said strips having afree end extending upwardly and beyond said heating means and detents, amovable bridge element, contacts mounted on said bridge to cooperatewith said stationary contacts, a central button for depressing saidbridge to engage the contacts thereon with said corresponding stationarycontacts and simultaneously for engaging said detents with said bridgeto retain the same in the oil-position, and for simultaneouslyconnecting said heating means, a central spring tending to force saidbridge and the contacts thereon to the oi-position, a plurality ofsprings for maintaining said bridge always substantially parallel withsaid base, said detents adapted to release said bridge when said bimetalstrips are being heated beyond a certain temperature, an insulatingplate having apertures therein disposed above said bridge, the free endsof said bimetal strips extending through said apertures so as to movefreely in one direction when said strips are bent by being heated, andmeans for manually shifting said insulating plate to bend said strips todisengage said detents, release said bridge, and disconnect saidcontacts independently of said heating means.

5. A multiple-pole protective switch comprising, in combination, astationary base, stationary contacts mounted on said base, a bimetalstrip for each circuit mounted on said base, means mounted on saidbimetal strips for heating the same, a detent on each of said bimetalstrips, said strips having a free end extending upwardly and beyond saidheating means and detents, a movable bridge element, contacts mounted onsaid bridge to cooperate with said stationary contacts, a cover, a pushbutton centrally mounted in said cover for depressing said bridge toengage the contacts thereon with the corresponding stationary contactsand simultaneously to engage said detents with said bridge to retain thesame in the onposition, and for simultaneously connecting said heatingmeans, a central spring mounted within said cover tending to force saidbridge and the contacts thereon to the ott-position, a plurality ofsprings intermediate said base and said bridge for maintaining saidbridge always substantially parallel with said base and also tending toforce said bridge to the oi-position, said detents adapted to releasesaid bridge When said bimetal strips are being heated beyond a certaintemperature, an insulating plate have apertures therein disposedintermediate said bridge and said cover, the free ends of said bimetalstrips extending through said apertures so as to move freely in onedirection when said strips are bent by being heated, and a slide buttonon said cover movably mounted therein toward and away from said centralbutton, said slide button having a knob thereon extending inwardly ofsaid cover and, when moved toward said central button, engaging saidinsulating plate to move the same laterally stationary contacts to bendsaid strips to disengage said detents and release said bridge formanually disengaging all or" said contacts independently of said heatingmeans.

6. A multiple-pole protective switch comprising, in coinbination, astationary base, stationary contacts mounted on said base, a bimetalstrip for each circuit mounted on said base, means mounted on saidbimetal strips for heating the same, a detent on each of said bimetalstrips, said strips having a free and extending upwardly and beyond saidheating means and detents, a movable bridge element, contacts mounted onsaid bridge to cooperate with said stationary contacts, a cover, a pushbutton centrally mounted in said cover for depressing said movablebridge to engage the contacts thereon with the corresponding stationarycontacts and simultaneously to engage said detents with said bridge toretain the same in the on-position, and for simultaneously connectingsaid heating means, a central spring mounted within said cover tendingto force said bridge and the contacts thereon to the oil-position, aplurality of springs intermediate said base and said bridge formaintaining said bridge always substantially parallel with said base andalso tending to force said bridge to the oil-position, said detentadapted to release said bridge when said bimetal strips are being heatedbeyond a certain temperature, an insulating plate having aperturestherein disposed intermediate said bridge and said cover, the free endsof said bimetal strips extending through said apertures so as to movefreely in one direction when said strips are bent by being heated, and aslide button on said cover and movably mounted therein toward and awayfrom said central button, said slide button having a knob thereonextending inwardly of said cover and, when moved toward said centralbutton, engaging said insulating plate to move the same laterally tobend said strips to disengage said detents and release said bridge formanually disengaging all of said contacts independently of said heatingmeans, the free ends of said bimetal strips automatically returning saidinsulating plate and said slide button to their neutral position whensaid slide button is released.

7. A multiple-pole protective switch comprising, in combination, astationary base of ceramic material having apertures therein, stationarycontacts mounted on said base and within said apertures, connectingterminals below said base and connected to said contacts, a bimetalstrip for each circuit mounted on said base, a resistance coil, aroundeach of said strips, one end of said coils being connected to saidstationary contacts, a detent on each of said bimetal strips andconnected to the other end of said resistance coil, said strips having afree end extending upwardly and beyond said resistance coils anddetents, a cover for said switch mounted on said base, a bridge elementof ceramic material Within said cover and movable relative to said base,contacts mounted on said bridge to cooperate with said stationarycontacts, a push button centrally mounted in said cover for depressingsaid movable bridge to engage the contacts thereon with thecorresponding stationary contacts and simultaneously to engage saiddetents with said bridge to retain the same in the on-position, and forsimultaneously connecting said other end of said resistance coils tosaid movable contacts, a central spring mounted within said covertending to force said bridge and the contacts thereon to theorfposition, a plurality of springs intermediate said base and saidbridge for maintaining said bridge always substantially parallel withsaid base and also tending to force said bridge to the off-position,said detents adapted to release said bridge when said bimetal strips arebeing heated beyond a certain temperature, an insulating plate havingapertures therein disposed intermediate said bridge and said cover, thefree ends of said bimetal strips extending through said apertures so asto move freely in one direction when said strips are bent by beingheated, said cover preventing said insulating plate from sliding oit thefree ends of said strips, and a slide button on said cover and movablymounted therein toward and away from said central button, said slidebutton having a knob extending inwardly of said cover and, when movedtoward said central button engaging said insulating plate to move thesame laterally to bend said strips to disengage said detents and releasesaid bridge for manually disengaging all of said contacts independentlyof said heating means, the free ends of said bimetal stripsautomatically returning said insulating plate and said slide button totheir neutral position when said slide button is released.

8. A multiple-pole protective switch comprising, in combination, astationary base of ceramic material hav ing apertures therein,stationary contacts mounted on said base and within said apertures,connecting terminals below said base and connected to said contacts, abimetal strip for each circuit mounted on said base, a resistance coilaround each of said strips, one end of said coils being connected tosaid stationary contacts, a detent on each of said bimetal strips andconnected to the other end of said resistance coil, said strips having afree end extending upwardly and beyond said resistance coils anddetents, a cover for said switch mounted on said base, a bridge elementof ceramic material having glazed cam surfaces for leading detentswithin said cover and movable relative to said base, contacts mounted onsaid ridge to cooperate with said stationary contacts, a push buttoncentrally mounted in said cover for depressing said movable bridge toengage the contacts thereon with the corresponding stationary contactsand simultaneously to engage said detents with said bridge to retain thesame in the oit-position, and for simultaneously connecting said otherend of said resistance coils to said movable contacts, a central springmounted within said cover tending to force said bridge and the contactsthereon to the oil-position, a plurality of springs intermediate saidbase and said bridge for maintaining said bridge always substantiallyparallel with said base and also tending to force said bridge to theoli-position, said detents adapted to release said bridge when saidbimetal strips are being heated beyond a certain temperature, aninsulating plate having apertures therein disposed intermediate saidbridge and said cover, the free ends of said bimetal strips extendingthrough said apertures so as to move freely in one direction when saidstrips are bent by being heated, said cover preventing said insulatingplate from sliding on" the free ends of said strips, and a slide buttonon said cover and movably mounted therein toward and away from saidcentral button, said slide button having a knob extending inwardly or"said cover and, when moved toward said central button, engaging saidinsulating plate to move the same laterally to bend said strips todisengage said detents and release said bridge for manually disengagingall of said contacts independently of said heating means, the free endsof said bimetal strips automatically returning said insulating plate andsaid slide button to their neutral position when said slide button isreleased.

9. ln combination with an electric motor having a housing, amultiple-pole protective switch mounted with in said housing andconnected to said motor, comprising a stationary base, stationarycontacts mounted on said base, at least one bimetal strip mounted onsaid base, a detent on said bimetal strip near the free end thereof,means on said bimetal strip for electrically heating the same when saidswitch is in the ori-position, a bridge element movable relative to saidbase, other contacts mounted on said bridge to cooperate with saidstationary contacts, resilient means tending to force said bridge andthe contacts thereon to the oilposition, means for depressing saidbridge so that the contacts thereon engage with the correspondinUstationary contacts and simultaneously to engage said detent with saidbridge to retain the same in the onposition, said detent being adaptedto release said bridge when said bimetal strip is heated beyond acertain temperature either by said electric heating means or thesurrounding temperature, and is thereby bent to disconnect saidcorresponding contacts, and independent manual means for mechanicallybending said birnetal strip to release said detent from said bridge torelease said bridge and disconnect said contacts.

References Cited in the le of this patent UNITED STATES PATENTS2,409,917 VOB HOOrn Oct. '22, 1946 2,483,646 Kitman Oct. 4, 19492,587,162 Ingwersen Feb. 26, 1952

